Really Simple Syndication (RSS) is an umbrella term for a handful of very similar eXtensible Markup Language (XML) syndication formats (e.g. RSS 1.0, RSS 2.0, Atom 1.0). An RSS Feed is an RSS/XML document that represents time-variant chunks of content published by an entity. Feeds may be of any type, though the most common are RSS feeds. For example, a typical RSS feed may be the entries published over time on a sports weblog (or “blog”) that covers a variety of sports, or a variety of teams within the same sport. The feed for such a blog may include a variety of entries, posted throughout the day, where the subject of each entry is a different news item or discussion topic that focuses on a particular sport or team. Feeds typically include references to outside sources of content, such as, in the example sports blog given above, image files of team logos, audio files including interview clips with players on a team, and/or video files includes highlights from a sporting event that a particular team participated in. These different types of content may be referred to as resources.
Typically, a user subscribes to one or more feeds by using an application known as an aggregator, or a feed reader. An aggregator combines the contents of multiple feeds for display on a single viewing location. That is, an aggregator allows a single user to access the content of a number of feeds, such as a feed from a sports blog, a feed including the day's weather forecast, a feed from a news source, and the like, without having to visit (e.g., in the user's web browser), the source of each of those disparate types of information.
RSS aggregators download all resources referenced in a feed in an arbitrary order. RSS aggregators typically go through two stages when downloading content. First, an RSS aggregator downloads and parses the RSS feed. If the RSS feed contains references to other downloadable files (e.g., thumbnail images, podcasts, video files, etc.), then the aggregator will subsequently download these referenced files. This is a standard workflow for aggregators.